Switching driver circuitry

Abstract

A switching driver circuit may have an output stage having an output switch connected between a switching voltage node and an output node. A switch network may control a switching voltage at the switching voltage node so that in one mode the switching voltage node is coupled to a positive voltage and in another mode the switching voltage node is coupled to ground voltage via a first switching path of the switch network. The circuit may also include an n-well switching block operable to, when the first switching voltage node is coupled to a positive voltage, connect the n-well of the first output switch to the switching voltage node, and, when the first switching voltage node is coupled to the ground voltage, connect the n-well of the first output switch to a first ground which is separate to the first switching voltage node and independent of the first switching path.

The invention claimed is: 
     
       1. A switching driver circuit for driving a load, the switching driver circuit comprising:
 an output stage comprising: an output node for outputting a driving signal to the load; and a first output switch connected between a first switching voltage node and the output node, wherein the first output switch comprises an n-well; and 
 a switch network operable to control a switching voltage at said first switching voltage node; 
 wherein the switching driver circuit is operable in a plurality of modes in which the first switching voltage is different in each mode, the plurality of modes comprising at least: a mode in which the first switching voltage node is coupled to a positive voltage; and a mode in which the first switching voltage node is coupled to a ground voltage supply via a first switching path of the switch network; and 
 an n-well switching block operable, when the first switching voltage node is coupled to a positive voltage, to connect the n-well of the first output switch to the first switching voltage node, and operable, when the first switching voltage node is coupled to the ground voltage supply, to connect the n-well of the first output switch to a first ground node at a ground voltage, where the first ground node is separate to the first switching voltage node and independent of the first switching path. 
 
     
     
       2. The switching driver circuit according to  claim 1  wherein the first switching path comprises at least a first supply switch with a terminal connected to the first switching voltage node and the first supply switch comprises an n-well; and wherein the n-well switching block is further operable, when the first switching voltage node is connected to the ground voltage supply, to connect the n-well of the first supply switch to the first ground node. 
     
     
       3. The switching driver circuit according to  claim 2  wherein the n-well switching block is further operable, when the first switching voltage node is connected to a positive voltage, to connect the n-well of the first supply switch to the first switching voltage node. 
     
     
       4. The switching driver circuit according to  claim 3  wherein:
 the output stage further comprises a second output switch connected between a second switching voltage node and the output node, wherein the second output switch comprises an n-well; 
 wherein the switch network is also operable to control the voltage at the second switching voltage node such that the second switching voltage is different in each mode; 
 wherein the n-well switching block is further configured to control a voltage supplied to n-well of the second output switch based on the second switching voltage. 
 
     
     
       5. The switching driver circuit according to  claim 4  wherein the n-well of the second output switch is connected to the n-well of the first output switch. 
     
     
       6. The switching driver circuit according to  claim 4  wherein in one mode of operation the second switching voltage node is coupled to the ground voltage supply via a second switching path that comprises at least a second supply switch of the switch network; and wherein the n-well switching block is operable, when the second switching voltage node is coupled to the ground voltage supply, to connect the n-well of the second supply switch to the first ground node, wherein the first ground node is independent of the second switching path. 
     
     
       7. The switching driver circuit according to  claim 5  wherein a terminal of the second supply switch is connected to the second switching voltage node and the second supply switch comprises an n-well and wherein the n-well switching block is further configured to control a voltage supplied to n-well of the second supply switch to be the same as the voltage supplied to the n-well of the second output switch. 
     
     
       8. The switching driver circuit according to  claim 1  wherein the n-well switching block comprises:
 a first n-well block switch for selectively connecting a first n-well voltage node to the first switching voltage node, wherein the first n-well voltage node is coupled to the n-well of the first output switch. 
 
     
     
       9. The switching driver circuit according to  claim 8  wherein the n-well switching block further comprises:
 a second n-well block switch for selectively connecting the first n-well voltage node to a supply select node; 
 a third n-well block switch for selectively connecting the supply select node to the first ground node; and 
 a fourth n-well block switch for selectively connecting the supply select node to a positive voltage supply node. 
 
     
     
       10. The switching driver circuit according to  claim 9  wherein the n-well switching block is configured such that, when the first switching voltage node is connected to the ground voltage supply:
 the first n-well block switch is open to disconnect the first n-well voltage node from the first switching voltage node; 
 the second and third n-well block switches are closed to connect the n-well node voltage to the first ground node; and 
 the fourth n-well block switch is open. 
 
     
     
       11. A switching driver circuit according to  claim 9  wherein the switching driver circuit is operable in a mode in which the first switching voltage node is coupled to a positive voltage substantially equal to a voltage of the positive voltage supply node and in which:
 the first n-well block switch is closed to connect the first n-well voltage node to the first switching voltage node; and 
 the second n-well block switch is open to disconnect the first n-well voltage node from the supply select node; and 
 the third n-well block switch, with the fourth n-well block switch closed so that the supply select node is coupled to the first ground node. 
 
     
     
       12. A switching driver circuit according to  claim 9  wherein the switching driver circuit is operable in a mode in which the first switching voltage node is coupled to a positive voltage which is more positive than a voltage of the positive voltage supply node and in which:
 the first n-well block switch is closed to connect the first n-well voltage node to the first switching voltage node; and 
 the second and third n-well block switches are open to disconnect the n-well voltage node from the supply select node; and 
 the fourth n-well block switch is closed to connect the supply select node to the positive voltage supply node. 
 
     
     
       13. The switching driver circuit according to  claim 9  wherein the output stage further comprises a second output switch connected between a second switching voltage node and the output node, wherein the second output switch comprises a n-well, and wherein the n-well of the second output switch is coupled to either the first n-well voltage node or the supply select node of the n-well switching block. 
     
     
       14. The switching driver circuit according to  claim 4  wherein said plurality of modes comprises:
 a first mode in which the network of switches is configured to connect the first switching voltage node to a positive input voltage supply and to connect the second switching voltage node to said ground voltage supply; 
 a second mode in which the network of switches is configured to connect the first switching voltage node to said ground voltage supply and to connect the second switching voltage node to a negative boosted voltage; 
 a third mode in which the network of switches is configured to connect the first switching voltage node to a positive boosted voltage and to connect the second switching voltage node to a negative boosted voltage. 
 
     
     
       15. The switching driver circuit according to  claim 14  further comprising a capacitor, and where the network of switches is operable such that the capacitor is charged between the positive input voltage supply and the ground voltage supply and selectively connected in series with the positive input voltage supply to provide the positive boosted voltage or connected in series with the ground voltage supply to provide the negative boosted voltage. 
     
     
       16. The switching driver circuit according to  claim 1  wherein said output stage is a first output stage and the switching driver circuit further comprises a second output stage and the switching driver circuit is configured to drive the load in a bridge-tied-load configuration between the first and second output stages. 
     
     
       17. The switching driver circuit according to  claim 1  wherein the load comprises at least one of: an audio output transducer; haptic output transducer; a piezoelectric transducer and a ceramic transducer. 
     
     
       18. An electronic device comprising the switching driver circuit according to  claim 1 .